From Dennis Patton:
The summer of 2015 has been one of the best in recent history. If I remember correctly, this will go down in the record books as the sixth wettest summer on record.
There is no comparison between this year and 2012, when we suffered through one of the hottest, driest periods in our history. As a result of a cooler, moister summer the lawns are in good shape with less dieback due to heat and drought.
But even with the nice weather some of us may have a few bare areas that need a little additional seed. Early September is the ideal time to overseed and thicken up that thinning stand with almost guaranteed success.
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Early September is the perfect time to fill in those bare spots or dead patches because the soil temperatures are high, nighttime temperatures start to cool off, and hopefully more rain begins to fall. This combination makes perfect conditions for quick germination and the establishment of turf from seed.
Soil preparation, seed selection, fertilization and irrigation are important keys to overseeding. To prepare the areas, core aeration and/or verticutting should be done to break up soil compaction.
Verticutting slices grooves in the soil, creating an area for grass seed to fall. This method is preferred for overseeding as it provides for the best and most even seed bed. Start by mowing the grass short (1 to 1.5 inches) and then verticut in one or two directions. Remove any debris from the lawn so good seed-to-soil contact is achieved.
High quality seed is a must for success. Avoid inexpensive seed that contains species such as creeping red fescue, fine leaf fescue, perennial, annual rye and annual bluegrass. These species may look good quickly after seeding, but they are sure to fail under stressful summer conditions.
Check the seed label to ensure you are getting good varieties of bluegrass or tall fescue. No other grass species will tolerate our local conditions. Some of the national brands found on the shelves are filled with inferior species for our area that will lead to failure.
Fertilizer is needed by new seedlings to help them establish and develop quickly. The existing grass also benefits from a September fertilizer application. Unlike the standard grass fertilizer that is high in nitrogen, new seed should be fertilized with a balanced fertilizer such as 13-13-13 or a high phosphorus product such as 10-20-10.
Phosphorus is a macronutrient that aids in the root development of young seedlings. Fertilizer should be applied at the rate suggested by a soil test (available through your local extension office) or a starter fertilizer should be used at the rate suggested on the bag.
Experience tells me that most people do not apply enough fertilizer when seeding as they are afraid of burning the new grass. In fact, the opposite happens as there is a lack of nutrition and the seedlings fail to grow. About four weeks after germination, apply a high nitrogen fertilizer such as 27-3-3 or 30-0-0 at labeled rates. This application should be repeated in mid-November to send the grass into winter strong.
Seeding is the next step and should be applied at half the seeding rate that is used for new lawns on bare soil. For tall fescue, the normal rate is 6 to 8 pounds per 1000 square feet, so the overseeding rate is 3 to 4 pounds per 1000 square feet. This should be broadcast over the prepared area.
The new lawn rate for bluegrass is 3 to 4 pounds per 1,000 square feet which makes the overseeding rate around 2 pounds. Fescue should germinate in about 10 days while bluegrass may take up to two weeks.
Water everything in and keep the seedbed constantly moist to ensure rapid germination. Begin with frequent, light irrigation and progress to deeper more infrequent watering as the seedlings become established.
Following these helpful hints should lead to success. Remember, the ideal window to overseed is very short. The greatest success is achieved by having the seed planted by Sept. 20. So you better get to work and let’s hope conditions will be favorable for good establishment.